Automated telephone and dialing devices ("Dial and Deliver") are now commonly employed to deliver pre-recorded voice messages to each party on a prepared list of telephone numbers. Such devices, under the control of a micro-processor, are able to deliver economically pre-recorded voice messages to great numbers of parties. These devices are often used to provide pre-recorded promotional messages, solicitations for sales, and emergency information.
However, the practical utility of automated telephone dialing devices and pre-recorded message delivery systems has been significantly decreased by the widespread use of automated telephone answering machines.
If a conventional automatic telephone dialing system dials the number of a telephone which is answered by an automatic answering apparatus, the pre-recorded message will not be delivered to the intended party. Lengthy pre-recorded messages may be played out even though no human is on the line to hear the message as may have been intended. Such a result obviously significantly lessens the cost-effectiveness and efficiency of using the automatic pre-recording message delivery system. Moreover, the pre-recorded message may never be delivered in the necessary time synchronization with the answering device to allow recording.
Prior systems directed to solve this problem are complex and unreliable. One method to serve this objective is to utilize the difference in frequency characteristics of a sound generated by a machine from the frequency characteristics generated by a human voice. This technique is very complex, and requires the design of highly complicated signal processing circuits. Some other systems have utilized the differences between the ways a telephone call is answered by a live party and the ways a message is recorded on an answering machine. For example, specific intervals of audio silence are looked for, during the first few seconds after a call is connected to detect a normal "Hello", which is usually one to four seconds of audio, followed by one to two seconds of silence. Recordings generally do not contain a pause after a "Hello." This difference enables the calling device to determine the presence or absence of a live person.
Prior art systems based on passive detection approach suffer from a significant degree of error. The duration of sound and silence to be tested, can only be optimized for a statistical average. Persons who do not answer within such statistical limits, will be considered machines and their call will be terminated. With recent advances in technology, announcement messages recorded on telephone answering devices are virtually indistinguishable from human voice, invalidating passive detection algorithms based on frequency characteristics of tape generated audio.
It is an object of this invention to provide an automatic system for the delivery of pre-recorded telephone messages which is able to efficiently and economically identify when it has reached a telephone answering device and not a human person.
It is a further object of this invention to provide an automated telephone system which, upon recognition on the line of an automated answering machine, is capable of delivering a pre-recorded message in time synchronization with the receive function of the answering machine so as to assure recording of the message by the answering apparatus.